Step 1

Preheat oven to 180°C. For the pastry, process flour, sugar and butter in a food processor until you have fine crumbs. Add egg yolk and 1 tablespoon iced water, then process until mixture comes together in a smooth ball. Enclose in plastic wrap and chill for 30 minutes.

Step 2

Roll the pastry out on a lightly floured surface to 3mm thick and use to line a greased 24cm loose-bottomed tart pan. Chill while you prepare the filling.

Step 3

Process marzipan, 20g butter, 1 egg, extra egg yolk, vanilla, lemon zest and flour in cleaned processor until smooth. Transfer to a bowl, cover and set aside.

Step 4

Melt the remaining 40g butter in a large frypan over medium-low heat. Add apples and sugar and cook, stirring, for 3-4 minutes until they start to soften. Stir in the sultanas, amaretti, cinnamon and lemon juice, then allow to cool. Pack apple mixture down into chilled tart shell, then spoon over the marzipan mixture, leaving gaps here and there. Lightly beat remaining egg, then brush over topping. Bake crostata for 1 hour 15 minutes or until golden and firm to touch - cover with foil if browning too quickly. Cool tart in the pan for 10 minutes, then remove from pan and transfer to a rack to cool completely.

Step 5

Meanwhile, for the custard, place eggs, sugar, flour and vanilla in a bowl and whisk to combine. Place bowl over a pan of simmering water and beat until thick. Remove bowl from heat and beat over a bowl of iced water until cool. Whisk in mascarpone, then cover surface closely with plastic wrap. Chill until needed.

Step 6

Dust tart with icing sugar, slice and serve with mascarpone custard.